Chunk #29 — RESULTS — Differential expression of signaling proteins in calcium, cyclic nucleotide and small GTPase 2nd messenger pathways in PCPs — cGMP signaling modules in LPC and CHC
cGMP signaling in the brain is predominantly triggered by nitric oxide (NO). In mature cortex, the synthetic enzyme NOS1 is expressed at high levels in a small set of SST+ long projection cells (LPCs) and much lower levels in several other GABA populations (Kilduff et al., 2011). We found that, in addition to NOS1, the neuronal L-arginine transporter Slc7a3 that supplies the substrate for NO synthesis (Friebe and Koesling, 2003) is also specific to LPC (Figure 5E); this tight co-expression may endow LPCs as the major source of cortical NO. As the key link from NO to cGMP production, the soluble guanylyl cyclase (sGC) functions as a strict heterodimer of α and β subunits (Friebe and Koesling, 2003). While Gucy1α2 is expressed at low levels across PCPs, Gucy1α3 and Gucy1β3 are highly enriched in CHC, PVBC and LPC cells but are nearly absent in SST/CR and VIP cells (Figure 5E). This suggests that cGMP signaling is prominent in the former three cell types but weak in the latter three populations. Consistently, cGMP-degrading Pde1a, 5a, 11a are also highly enriched in
